Study on the surface crack propagation mechanism of coal and sandstone subjected to cryogenic cooling with liquid nitrogen

Du, Menglin; Gao, Feng; Cai, Chengzheng; Su, Shanjie; Wang, Zekai

doi:10.1016/j.jngse.2020.103436

Cited by 33 publications

(11 citation statements)

References 28 publications

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“…After 140 freeze–thaw cycling tests, the NMR T 2 spectrum change rate is 197% and the average change rate is 1.41% . The NMR T 2 spectrum change rate after the interaction of tight sandstone and liquid nitrogen ranges from 1.19 to 12.94% . Therefore, the conclusion of this manuscript is reliable.…”

Section: Resultsmentioning

confidence: 61%

“…In the 1990s, liquid nitrogen was used as a fracturing fluid for improving oil and gas production, with significant effects. , Liquid nitrogen cooling has a cold impact on the reservoir. The mineral particles and rock cement shrink sharply owing to the sudden temperature drop, reducing the toughness of the rock and increasing its brittleness. − When the temperature drops sharply, a large tensile stress is generated inside the rock, leading to a change in the rock pore throat structure and the generation of microcracks. − In addition, liquid nitrogen will induce the formation of secondary fractures perpendicular to the main fracture, and the secondary fractures will propagate and connect to each other, significantly increasing the permeability of the reservoir. − …”

Section: Introductionmentioning

confidence: 99%

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Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO₂ Cooling in Shale Oil Reservoirs

Huang

et al. 2021

Energy Fuels

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The interactions between CO2 and reservoirs under low-temperature cooling conditions can change the pore throat characteristics of the corresponding rocks. In this work, the interaction mechanisms between liquid CO2 cooling and pore throat systems of shale were researched using nuclear magnetic resonance (NMR) technology. Five typical shale core samples were selected and subjected to liquid CO2 cooling experiments under different conditions. Furthermore, the change ranges of the pores were quantitatively calculated based on the NMR T 2 spectra. The results indicate that the overall pore throat system of the shale changes after liquid CO2 cooling. The factors influencing the degree of change are the pore throat structure, liquid CO2 cooling temperature, and cooling time. The degree of change for different pores are related to the relative contents of the pores in the initial state. When the liquid CO2 cooling experiments comprise one, two, and three iterations, the average overall increase in the NMR T 2 spectrum are 2.56, 5.81, and 8.97%, respectively, and the average increase of the smaller pores are 0.77, 0.92, and 1.84%, respectively. The overall pore throat system changes greatly with an increase in the liquid CO2 cooling times, and the degree of change in the smaller pores increases. When the liquid CO2 cooling temperature of core sample A2 ranges from −30 to −20 °C, the increase in the T 2 spectrum is between 3.57 and 2.20%. When the liquid CO2 cooling temperature of core sample B2 is increased from −30 to −20 to −10 °C, the increases in the T 2 spectrum are 2.97, 2.90, and 2.79%, respectively. As the temperature of the liquid CO2 increases, the change in the overall pore throat system is weakened. The smaller pores change more obviously after liquid CO2 cooling within a certain low-temperature range. The degree of change of the larger pores is less affected by temperature.

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Section: Resultsmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO₂ Cooling in Shale Oil Reservoirs

Huang

et al. 2021

Energy Fuels

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“…Liquid nitrogen is at an ultralow temperature; LN 2 fracturing causes changes in the physical and mechanical properties of the rock. , According to macroscopic phenomenological continuum mechanics, the stress–strain relationship of damaged coal and rock under one-dimensional cyclic stress is as follows: where ε is the strain; E and E n are the initial elastic modulus of coal and the elastic modulus after n cylces of loading and unloading, respectively; D is the damage variable; ω is the angular velocity; t is the time.…”

Section: Ln2 Fracturing Coal Rock Mass In the Field Of Oil And Gas Ex...mentioning

confidence: 99%

“…Mechanical Properties of Coal and Rock Mass Damaged by LN 2 Fracturing. Liquid nitrogen is at an ultralow temperature; LN 2 fracturing causes changes in the physical and mechanical properties of the rock 148,149. According to macroscopic phenomenological continuum mechanics, the stress−strain relationship of damaged coal and rock under one-dimensional cyclic stress is as follows:…”

mentioning

confidence: 99%

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

et al. 2022

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Liquid nitrogen (LN 2 ) fracturing is an anhydrous fracturing technology that enhances coal permeability and supports unconventional oil and gas exploitation. In this Review, we provide a systematic review of five aspects of LN 2 fracturing. They are the history of the technology's development, research topics, factors influencing fracturing efficiency, fracturing mechanism, and engineering processes and systems. Liquid nitrogen fracturing transforms coal and rock pore structure through mechanisms such as low temperature, freeze−thaw damage, and gas expansion. It changes coal and rock mechanical properties and improves the pore penetration and efficiency of unconventional oil and gas extraction. However, in-depth studies are still required in many areas. They include theoretical studies of twophase nitrogen flow in coal and rock, development of technical equipment to support field operations, and plans to monitor and evaluate fracturing efficiency. On the basis of the advances in LN 2 fracturing research and the challenges, we conclude that future research should focus on multiphase flow and field equipment and technology.

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“…The shale pore structure undergoes significant alteration after freeze-thaw cycles, and some micro-pores are aggregated to form micro-and macro-cracks [3]. Although LN cooling increases permeability [2,5,6], it is less effective for sandstone than it is for other sedimentary rocks [7,8]. The surface micro-structure of rocks raises the Leidenfrost point, thus shortening the duration of film boiling and increasing the rate of cooling.…”

Section: Introductionmentioning

confidence: 99%

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

et al. 2021

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In cryogenic fracturing, a rock surface exposed to cryogenic fluids undergoes a large thermal gradient, and the resultant local tensile stress overcomes rock strength and initiates fractures. This study investigates the development of cracks generated from the cryogenic treatment of a borehole under no external confining stress on specimens. The experiments were performed on transparent PMMA specimens to observe fracture proliferation around boreholes. Liquid nitrogen was flowed through the boreholes to cool the borehole surface. The results show that initial fracture growth is characterized by abrupt starts and stops, and as the fracture propagates outward, the growth appears more continuous. In an early stage, horizontal/radial fractures and vertical fractures are the defining patterns. Horizontal fractures tend to be separated by a specific exclusion distance (i.e., spacing between cracks). While distinct horizontal/vertical fractures and exclusion distance manifest themselves at an early stage, fractures resulting from fracture interactions and curvatures can develop into complex shapes at later stages. Cryogenic thermal loading induces distinctively curved fractures. The tendency of curvature may prevent greater penetration. An increase in the borehole pressure during liquid nitrogen flow, however, can lessen fracture tortuosity and facilitate radial propagation. A high flow pressure and rate are also advantageous in that they accelerate cooling and fracture propagation.

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Study on the surface crack propagation mechanism of coal and sandstone subjected to cryogenic cooling with liquid nitrogen

Cited by 33 publications

References 28 publications

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO₂ Cooling in Shale Oil Reservoirs

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO₂ Cooling in Shale Oil Reservoirs

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

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Study on the surface crack propagation mechanism of coal and sandstone subjected to cryogenic cooling with liquid nitrogen

Cited by 33 publications

References 28 publications

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO2 Cooling in Shale Oil Reservoirs

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO2 Cooling in Shale Oil Reservoirs

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

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Product

Resources

About

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO₂ Cooling in Shale Oil Reservoirs

Experimental Study on Changes in Pore Throat Systems Owing to Liquid CO₂ Cooling in Shale Oil Reservoirs